Lockstitch sewing machines



Dec. 30, 1958 R. G. PALMBACH 2,866,425

LOCKSTITCH SEWING MACHINES Filed June 14, 1955 5 Sheets-Sheet 1 I3 I I2I v :23: I 34 i II I: JUIIDVE i all I i [LL-fi I !s I I15 5 Dec. 30,"1958 R. G. PALMBACH LOCKSTITCH SEWING MACHINES Filed June 14, 1955 5SheetS-Shget 2 III" Dec. 30, 1958 PALMBACH 2,865,425

LOCKSTITCH SEWING MACHINES Filed June 14, 1955 F IGQG 5 Sheets-Sheet 30, 1958 R. G. PALMBACH 2,866,425

LOCKSTITCH SEWING MA CHI NES Filed June 14, 1955 FIGJO e ocLocK POSITION5 Sheets-Sheet 5 DIRECTION OF ROTATION FIG."

United States Patent Cfiice 2,866,425 Patented Dec. 30, 1958 LOCKSTITCHSEWENG MACHINES Richard G. Palmbach, Lombard, Ill., assignor to UnionSpecial Machine Company, Chicago, Ill., a corporation of IllinoisApplication June 14, 1955, Serial No. 515,514 6 Claims. (Cl. 112-182)This invention relates to a lockstitch sewing machine having a rotaryhook of the type adapted to be revolved about a vertical axis or an axisperpendicular to the work supporting surface of the machine, at anangular speed which is twice that of the shaft which drives thecooperating needle.

In machines of the character indicated, difficulties have beenencountered in insuring the proper passage of loops of needle thread ofdifferent weights around the bobbin case and through the spacesmomentarily provided between various shoulders and detents. Thesedifficulties have been particularly pronounced when the machines havebeen supplied with a relatively heavy needle thread, since the heavierthreads are not so readily carried across the upper face of the bobbincase. The tendency of the upper leg of the needle thread loop to lagbehind makes it diflicult to bring it at the proper time to the gaptemporarily provided between the shoulders on the bobbin case and itsdetaining means and also to the point at which the looper opener actsupon the bobbin case. As a result, frequent breakage of the threadoccurs because it is held at one point or another at the time it isbeing rapidly pulled up by the takeup mechanism.

In an effort to provide the required timing for the passage of a heavythread between the shoulders and detaining means mentioned above, theaction of the hook opening mechanism has been delayed for about incertain machines, but this has left inadequate time for the withdrawalof the usual opening finger before the thread must be pulled betweenthis finger and the cooperating surface on the bobbin case. Otherexpedients which have heretofore been adopted involve a change in thetiming of the needle thread takeup means and an a increase in the takeupaction. These changes have also proved objectionable. Moreover, inadjusting a machine by these expedients to provide the proper timing fora relatively heavy thread the timing is wrong for a lighter thread.

Also to insure proper cooperation between the needle and the looper, itis desirable for proper stitch formation to provide for adjustment of aneedle guard element carried by the looper to accommodate needles ofdifferent guages, as when the machine is required to deal with light andheavy needle threads at different times.

An important object of the present invention has been to provide alockstitch sewing machine with a rotary book of the character indicatedhaving special means for so retaining and directing the needle threadloop that its upper leg will be carried properly across the top of thebobbin case, regardless of the weight of the thread being employed atany particular time. The preferred arrangement is such that a minimum ofresistance is offered to the movement of the thread across the varioussurfaces which it must engage in its passage round the bobbin case. Itis also preferably such that the top legof the loop is passed across thetop of the bobbin case substantially simultaneously and in parallelismwith the pasage of the lower leg across the bottom of the bobbin case oreven slightly in advance of the latter. With hooks as heretoforeconstructed, the top leg of the loop has lagged considerably behind thelower leg in its movement across the bobbin case, particularly when arelatively heavy thread has been used.

The improved hook of the present invention has a loop seizing beak theupper and lower portions of the outer surface of which incline inwardlytoward the axis of the hook from a substantially median line extendinglengthwise of the beak. In this way the upper and lower edges of thebeak are positioned as closely as possible to the top and bottomperipheral edges of the bobbin case retained within the hook. Now inconjunction with this beak formation the hook is provided with a needlethread loop retaining element which projects outwardly and upwardly fromthe inclined upper portion of the outer surface of the beak at a pointadjacent the base of the beak where it merges with the main verticalwall of the hook body. The point of connection of the element or spurwith the hook is substantially midway between the usual raceway in thehook and the top edge of the hook beak. It is also so located that theraceway is substantially midway between this point of connection of thespur and the bottom of the bobbin case. The arrangement of the spur issuch that it tends to hold the portion of the thread loop which extendsacross the outer face of the beak in a substantially vertical positionuntil the beak of the hook has moved through an arc of somewhat morethan after entering the needle thread loop.

Another object has been to provide a needle guard on a rotary hook ofthe character indicated which may be readily adjusted for cooperationwith needles of different gauge without the necessity of bending themetal of which the guard is formed. The arrangement is such that allportions of the guard maintain their proper relation to the needles ofdifferent gauge when appropriately adjusted. Thus the guard performs itsneedle deflecting and positioning function in the desired manner andenables the formation of the desired needle loop for seizing by the beakof the hook, regardless of the gauge of the needle and the weight of thethread being employed.

Other objects, features, and advantages of the invention will appearfrom the detailed description of an illustrative embodiment of the samewhich will now be given in conjunction with the acompanying drawings, inwhich:

Fig. 1 is a vertical sectional view through a portion of the worksupport of a sewing machine and through one of a pair of vertical axisrotary hook units incorporating the invention, embodied in the machine,the cooperating needles also being shown;

Fig. 2 is an exploded perspective view of the parts forming one of thevertical axis hooks;

Fig. 3 is a perspective view of one of the rotary books with the partsthereof assembled;

Fig. 4 is a vertical sectional view through the main body portion of oneof the rotary hooks;

Fig. 5 is a bottom view of one of the rotary hooks showing theadjustable mounting of a needle guard;

Figs. 6, 7, 8,' and 9 are plan views of the pair of verticall axisrotary hooks embodied in the illustrative machine, together with acooperating throat plate partly broken away and shown in section; theseviews show the books at different positions in their cycle of operation;

Fig. 10 is a perspective view of the hook assembly and illustrates theposition of the needle thread loop at a point in the cycle of operationof the hook;

Fig. 11 is a bottom View of a preferred form of throat plate embodied inthe machine; and

Fig. 12 is a vertical, transverse sectional view through the throatplate, taken along the line 12-12 of Fig. 11.

The sewing machine embodying the invention may be of the generalconstruction illustrated in the patent to Quist No. 2,329,484, grantedSeptember 14, 1943. It includes a pair of vertical axis hook units inthe work supporting base of the frame and a needle bar in the head ofthe overhanging arm of the frame provided with a pair of needlesarranged for reciprocation toward and through the work support forcooperation with the hook units. Also, as disclosed in the Quist patent,the needle bar actuating mechanism may include means for imparting aneedle feed movement to the needles as they are engaged with the work onthe work support.

Referring now particularly to Fig. l of the drawings, there isillustrated a pair of thread carrying needles arranged to be carrieddownwardly through a work supporting surface 11 provided on the machineframe. Each needle is arranged to cooperate with a vertical axis hookunit, only one of which is illustrated in Fig. l and designated 12. Afour-motion feed dog 13, which may be operated through connections ofthe character illustrated in said Quist patent, serves to advance thework in the course of switch formation. Each hook unit has a housing 14adapted to support the operating parts of the unit and also to provide alubricant reservoir for the automatic lubrication of the wear receivingparts. As disclosed in the above mentioned Quist patent, each unit ispreferably arranged for adjustment on the frame of the sewing machine tovary the spacing of the lines of stitching formed by the pairs ofneedles and cooperating rotary hooks. Within suitable extensions of eachhousing 14 there is journaled a vertically disposed hook shaft 15arranged to be driven through a spiral gear 16 secured to the shaftwhich cooperates with a spiral gear 16a (Fig. 6) on the main drive shaft16b in the base of the machine. The relationship between the gear 16 andthe driving gear 16a on the main shaft is such that the hook shaft 15 isrotated at twice the angular speed of the drive shaft. Secured to theupper end of the shaft 15 is a hook assembly 17 which includes a rotarycomponent 18 that is revolved with the shaft and is provided with aneedle-thread loop-seizing beak 19. Hub 18a of the rotary component issecured to the shaft by set screws 18b. The rotary component 18 alsocarries a needle guard 20 arranged to cooperate with the needle 10 justprior to the seizing of the needle thread loop by the beak 19.

Rotary component 18 of the hook unit is cup-shaped and arranged toreceive a stationary bobbin case 21 having a circumferentially extendingrib formation which cooperates with a raceway in the rotary component.Bobbin case 21 is held against rotation with the rotary component bymeans of a projection 22 at the top of the bobbin case which cooperateswith a downwardly extending rib 23a of a throat plate 23 mounted in anopening in the work supporting surface 11 of the machine frame. Rib 23ais cut away in a region 23b to receive the projection 22 of the bobbincase and is arranged to provide a pair of spaced shoulders forcooperation with the projection 22. The arrangement is such that thebobbin case may be turned through a small angle to provide a gap at oneside or the other of the projection 22. It will be understood that asthe rotary component 18 is revolved, it will normally tend to drag thebobbin case in the same direction so that one edge of projection 22 isurged against one of the shoulders provided on the rib 23a. However,when it is desired to draw the upper leg of the needle thread loopupwardly between the projection 22 and the cooperating shoulder on rib23a, the bobbin case is shifted slightly in a direction counter to thedirection of revolution of the hook. For this purpose a finger 24 isarranged to cooperate with a projection 25 on the bobbin case. Finger 24is adjustably mounted on an arm 26 secured by means of a screw 27a tothe upper end of a rock shaft 27 mounted in the hook frame 14. At thelower end of shaft 27 there is secured thereto an arm 28 which ispivotally connected with one end of a pitman 29 having a strap portioncooperating with an eccentric 30 adjacent the lower end of shaft 15. Thearrangement is such that the hook opening finger 24 is moved intoengagement with the projection 25 of the bobbin case to turn the latterslighly at the time in the cycle of rotation of the hook that the upperleg of the needle thread loop is in vertical alignment with the notch orcutout portion of the rib 23a, so that this leg of the thread may bepulled upwardly through the gap and subsequently passed over theprojection 22 of the bobbin case.

Considering the construction of the hook in greater detail, by referenceto Figs. 2 to 5 inclusive, the main body portion 18 of the rotarycomponent has a generally cylindrical contour. However, in the region ofthe beak 19 it is provided with an upward extension, the outer face 31of which is inclined inwardly toward its top in the direction of theaxis of the hook. This inwardly inclined surface 31 continues throughoutthe length of the beak and serves to position the top edge 32 of thebeak as close as possible to the bobbin case and relatively near the topof the latter. The longitudinal center line 33 of the beak forms acontinuation of the top edge of the cylindrical portion of the bodymember 18 but is inclined upwardly as shown. Beneath this center linethe beak is provided with an inwardly inclined surface 34 which servesto position the lower edge of the beak as close as possible to thebobbin case. A radially extending shoulder 35 provided around the innersurface of the hook body 18, over a circumference of about forms thelower edge of a hook raceway the top edge of which is provided by theunderside of a removable semi-annular plate 36 adapted to be attached tothe body 18 by means of screws. Interrupted rib formation-'37 extendingaround the bobbin case is adapted to ride in the raceway so formed.

Adjacent the base of the beak 19, where it joins the main body of thehook, the surface 31, which is otherwise curved circumferentially, isflattened in an area 38 and at this point there is provided an outwardlyand upwardly extending thread retaining element or spur 39. The latterhas a shank 40 inserted in a hole formed perpendicular to the flattenedsurface 38. A flange 41 on the spur rests upon such flattened surface.The spur may be held in the opening by any suitable means, such as thefriction created by a tight press fit. Outwardly of the flange 41 thespur is provided with a groove 42 which extends around the circumferenceof the pin like spur. The arrangement is such as to provide a number ofconditions adapted to bring about the desired movement of the needlethread loop across the top and bottom faces of the bobbin case. The spuris positioned about inwardly fro-m the point of the hook beak. Itsforwardmost point is substantially vertically above a shoulder 43provided by the merging of the lower edge of the beak with thecylindrical portion of the body 18 of the hook. The outer end of theopening in which the stem 40 of the spur is inserted is positioned aboutmidway between the top of the beak of the hook and the racewaydescribed. This raceway, moreover, is positioned about midway betweenthe outer end of the opening which receives the stem 40 and the bottomof the bobbin case. The axis of the spur 39 extends outwardly in aradial direction from the axis of the hook and is inclined upwardly atan angle of about 30. This serves to position the uppermost part of thegroove 42 near the top of the portion 31 of the hook body so that, aswill appear more clearly hereinafter, the upper leg of the needle threadloop extends in a substantially straight line from the top of the spurto the bottom of the throat plate at the stitching point.

As best shown in Fig. 5 the needle guard 20, which extends upwardly fromthe base of the main body of the hook in a region below and forwardly ofthe hook beak, is carried by and preferably formed integrally with aplate 44 having an opening surrounding the hub 18a of the body of thehook. This plate is attached at one point by means of a screw 45 to theunderface of the hook body and it is attached at another point by ascrew 46. When the screws are loosened the plate may be pivoted aboutthe axis of screw 45 to the extent permitted by an elongated slot 47 inplate 44 which receives the shank of screw 46. If desired such pivotaladjustment could be provided by an enlarged circular opening cooperatingwith screw 46 in lieu of the elon gated opening. It will be seen fromFig. 5 that through the pivotal adjustment of the plate 44 about theaxis of screw 45 the needle guard may be shifted inwardly or outwardlyto a limited extent in relation to the axis of the hook. Plate 44 isprovided with an enlarged central opening 48 surrounding the hub 18a toallow for such adjustment. It should be noted in connection with theforegoing that in the adjustment of the needle guard the radial movementof end 20a thereof is greater than that of the end 20b thereof. This isdesirable since,

in the rotation of the hook, the portion 20b comes opposite the needlefirst and the beak of the hook is not encountered until about themid-portion of the needle guard is engaged with or is positionedopposite the needle. The curvature of the needle guard is such that itsmid-portion extends radially outward slightly more than either endportion. This insures the desired outward deflection of the needle toprevent interference with the passage of the hook beak. This function ofthe needle guard must be achieved without interfering with the castingof a small loop by the needle as it is moved upwardly a slight distancefrom its lowermost position so that the loop may be seized by the beakof the hook.

The bobbin case is adapted to receive a spool or bobbin 49 suitablysupplied with the locking thread for the stitching produced by theoperation of the machine. This spool has a central opening arranged tofit over a tubular center post 50 extending upwardly within the bobbincase and the spool is retained in position by means of a spring urgedarm 5th: pivotally mounted at the top of the post 50.

Turning now to Figs. 6 to 9 inclusive, the operation of the hook in thecourse of a loop-seizing revolution is illustrated. In these figures twohooks are shown, one adapted to cooperate with each of the needles 10.Since these hooks are of identical construction, but positioned inreverse relation to each other, it will suffice to consider the actionof one. For convenience the description will be directed to the actionof the lefthand hook. In Fig. 6 the hook is shown in the position itassumes just as the point of the loop-seizing beak is ready to enter theneedle thread loop. The needle thread is not shown in Fig. 6 but thebobbin thread 52 is indicated as extending from the end of a tensioningspring element 51 (Fig. 2) on the outer face of the bobbin case to itspoint of connection with the work being advanced over the throat plate23. The path of thread 52 is such that is is above the beak of the hookas the latter approaches the loop-seizing position.

In Fig. 7 the beak 19 of the hook is shown approaching the six oclockposition, i. e. 180 from the point at which it has entered the needlethread loop. The needle thread is indicated at 53 and it wil be notedthat at this time it extends from the needle 10 along a substantiallystraight line to the spur 39. At the point where the thread crosses thebobbin case detaining rib 23a of the throat plate the thread isapproaching alignment with a gap between the projection 22 of the bobbincase and the forward shoulder of the passage through the rib 23a. Also,it will be noted that the projection 22 has been shifted at leastpartially counter to the movement of the rotary hook, by the action ofthe opening finger 24. Thus the upper leg of the needle thread loop isat this 6 time about ready to pass upwardly through the gap, so that itmay, from this point on, be carried freely across the top of the bobbincase.

In Fig. 8 the point of the beak of the hook has progressed to a positionabout 210 from the point at which the needle thread loop was seized. Thegap between projection 22 and the forward shoulder on rib 23a is stillopen so that the upward movement of the needle thread loop through thegap may be continued up to this point. The looper opening finger 24,however, is being restored toward the right so that the gap is beginningto close and it becomes fully closed before the point of the beak of theloop er reaches the position shown in Fig. 9, which is about 240 fromthe needle. At this position the finger 24 is a slight distance from theprojection 25 and the needle thread loop, which is being drawn upwardlyby the takeup mechanism of the machine, is free to pass between the arm24 and projection 25 of the bobbin case. As has been explained above, ifthe timing of the hook opening finger were such as to hold the gapbetween projection 22 and the shoulder on rib 23a appreciably longerthan is indicated in Fig. 8, there is danger that the opening fingerwill not be retracted fast enough to permit the thread loop to passbetween it and projection 25. If the thread is nipped at this point itis likely to be severed by the rapid pulling action of the takeupmechanism.

Fig. 10 illustrates the course of the needle thread loop both above andbeneath the bobbin case. The hook in this view is substantially in theposition indicated in Fig. 7. It will be noted that the needle threadloop 53 has its upper leg 53U extending across a portion of the top ofthe bobbin case and has its lower leg 53L correspondingly positionedacross a portion of the bottom of the bobbin case. The intermediateportion 53a of the thread extends substantially vertically along theouter face of the hook adjacent the base of the beak.

In Figs. 11 and 12 there is illustrated a preferred form of throat plateemployed in connection with the invention. The throat plate 23 isprovided with feed dog receiving openings 54 separated by a central rib55. The latter has its longitudinal edges bevelled as indicated at 55ain Fig. 12. Similarly the outer longitudinal edges of the openings 54have their lower portions bevelled as indicated at 56. This bevelling ofthe edges of the openings which cooperate with portions of the feed dogserves to eliminate, or at least minimize, the accumulation and packingof lint in the groove at the top of the feed dog. Itv should also benoted in connection with Fig. 11 that the cut-away portions or openingsof the two ribs 23a, which are indicated at 23b, are not in directtransverse alignment. This is to provide the offset relationship,indicated in Figs. 6 to 9 inclusive, for correct action with theprojections 22 of the bobbin cases.

While a preferred embodiment of the invention has been disclosed inconsiderable detail, it will be understood that various modificationsmay be made within the scope of the appended claims.

What is claimed is:

1. In a lockstitch sewing machine having a horizontally disposed worksupporting surface, a thread carrying needle reciprocable through saidsurface, a cup-like rotary hook cooperating with said needle in stitchformation mounted for rotation below said surface about a vertical axis,and driving means for reciprocating said needle and rotating said hookand arranged to impart two revolutions to said hook for eachreciprocation of said needle, a loop seizing beak on said hook the topportion of the outer surface of which is inclined inwardly toward theaxis of the hook, said beak merging on its lower side with a loopretaining shoulder at the base of the beak and adjacent the bottom ofthe hook, said needle during its reciprocation passing outside of thecircular path of the tip of the loop seizing beak, a bobbin case mountedwithin said rotary hook and extending upwardly therefrom and a'spurextending outwardly from the inwardly inclined surface of said hook"beak adjacent the base thereof, the outermost point on said spur beingsubstantially within the confines of the circular path of the tip of theloop seizing beak, the forward side of said spur being arranged toengage the needle thread loop and carry the upper leg thereof across thetop of said bobbin case.

2. In a lockstitch sewing machine adapted for use with both light andheavy threads carried by needles of different diameter, said machinehaving a work support with a horizontally disposed work supportingsurface, a reciprocable needle bar adapted to receive a thread carryingneedle of any desired diameter and to reciprocate the same through saidwork supporting surface, a cup-like rotary hook cooperating with saidneedle in stitch formation mounted for rotation below said surface abouta vertical axis, and driving means for reciprocating said needle androtating said hook and arranged to impart two revolutions to said hookfor each reciprocation of said needle, a loop seizing beak on said hookthe top portion of the outer surface of which is inclined inwardlytoward the axis of the hook, said needle during its reciprocationpassing outside of the circular path of the tip of the loop seizingbeak, a bobbin case mounted within said rotary hook and extendingupwardly there from, a spur extending outwardly from the inwardlyinclined surface of said hook beak adjacent the base thereof, theoutermost point on said spur being substantially within the confines ofthe circular path of the tip of the loop seizing beak, the forward sideof said spur being arranged to engage the needle thread loop at a pointnear the plane of the top of the bobbin case and carry the upper leg ofthe loop across the top of said bobbin case, a needle guard carried bysaid hook for deflecting the needle in advance of the loop seizingaction of said beak, and means for adjustably mounting said.

needle guard on the bottom of said hook to accommodate needles ofdifferent diameter.

3. In a lockstitch sewing machine adapted for use with both light andheavy threads carried by needles of different diameter, said machinehaving a work support with a horizontally disposed work supportingsurface, a reciprocable needle bar adapted to receive a thread carryingneedle of any desired diameter and to reciprocate the same through saidwork supporting surface, a cup-like rotary hook cooperating withsaidneedle in stitch formation mounted for rotation below said surface abouta vertical axis, and driving means for reciprocating said needle androtating said hook and arranged to impart two revolutions to said hookfor each reciprocation of said needle, a loop seizing beak on said hookthe top portion of the outer surface of which is inclined inwardlytoward the axis of the hook, said beak merging on its lower side with aloop retaining shoulder at the base of the beak and adjacent the bottomof the hook, said needle during its reciprocation passing outside of thecircular path of the tip of the loop seizing beak, a bobbin case mountedwithin said rotary hook and extending upwardly therefrom, a spurextending outwardly from the inwardly inclined surface of said hook beakadjacent the base thereof, the outermost point on said spur beingsubstantially within the confines of the circular path of the tip of theloop seizing beak, the forward side of said spur being arranged toengage the needle thread loop and carry the upper leg thereof across thetop of said bobbin case, a needle guard carried by said hook fordeflecting the needle in advance of the loop seizing action of saidbeak, and means for adjustably securing said needle guard to the bottomof said hook to accommodate needles of different diameter, said needleguard having a plate-like base applied to the bottom of the rotary hook,and said securing means comprising screws at least one of whichcooperates with an enlarged opening in said plate-like base to providefor adjustable securernent of the latter.

4. In a lockstitch sewing vmachine of the character set forth in claim1, said spur being of cylindrical, pin-like form.

5. In a lockstitch sewing machine of the character set forth in claim 4,said cylindrical, pin-like spur having an annular groove around the sameintermediate its ends to retain said thread loop, and said spurextending outwardly and upwardly from the inwardly inclined surface ofsaid hook beak to substantially the level of the top of the bobbin case.

6. In a lockstitch sewing machine of the character set forth in claim 1,a fixed shoulder on said machine adjacent said work supporting surfacein the region of the reciprocation of said needle, a cooperatingshoulder on said bobbin case for detaining the bobbin case againstrotation with said hook, and means operable intermittently for turningsaid bobbin case counter to the direction of rotation of said hook toprovide a gap between said shoulders when the tip of said loop seizingbeak is not more than from the position in which it enters the needlethread loop, said spur being so located as to insure presentation of theupper leg of said loop at said gap when the bobbin case is turned bysaid intermittently operated means.

References Cited in the file of this patent UNITED STATES PATENTS

